Much of the soil in Oklahoma, including Moore, is red clay -- a porous substance that makes foundations settle and basements and underground tornado shelters leak. “That’s the reason we don’t have basements,” said Tom Bennett of Tulsa, past president of the National Storm Shelter Association. In greater Oklahoma City, which includes Moore, only 3.5 percent of homes have basements, according to Reuters.

But it wasn’t just the ground under residents’ feet that was to blame. The region’s politics and economy also were factors.

“This is a red state,” said state Rep. Richard Morrissette, D-Oklahoma City, who has introduced several unsuccessful bills in the state Legislature to require so-called “safe rooms,” shelters or anti-tornado construction in homes and trailer parks. “People don’t like anything that is mandated. They don’t like it when the government says they have to do something.”

That makes Oklahoma similar to other states in Tornado Alley. “I am unaware of any jurisdiction that requires safe rooms in private homes,” said Corey Schultz, a Kansas architect who specializes in building safe rooms for schools. And only one state – Alabama – requires them in schools, he said.

Though the mayor of Moore said Wednesday he now wants the city to require shelters in private homes, Oklahoma, like other states prone to tornadoes, prefers to encourage the construction of shelters. The state has emphasized using federal funds to underwrite the optional construction of specially reinforced, above-ground “safe rooms” inside private homes rather than community tornado shelters.

But building a steel room on a concrete slab adds thousands to the price of a new home in a market where a typical property is worth $108,000. And for homeowners, spending $2,500 and up to add tornado protection to existing homes often isn’t feasible without assistance in a state where the median income is $44,000 -- $8,000 below the national figure.

That’s a tough sell, even though it could mean the difference between life and death, said Bennett, the former president of the storm shelter association.

“In-residence’ safe rooms’ are the way to go,” he said. The rooms are built to withstand EF 5 tornadoes, with winds of 250 mph – in excess of the 210 mph recorded in Moore. “But half the population can’t afford it or doesn’t have a place to put it because they live in apartments.”

FEMA, which has programs to offset the costs, estimates it costs between $6,600 and $8,700 for a steel-reinforced 8-by-8-foot room, and much more for a larger space.

In 2012, the state launched a new program to make construction of the rooms less costly. SoonerSafe pays homeowners 75 percent of the cost of building a safe room, up to $2,000. But again, the money is federal, pulled from the state’s unused FEMA funds, and winners are chosen via lottery. In 2012, 16,000 homeowners applied, and 500 “won” the reimbursements via random drawing.

“Oklahoma’s SoonerSafe Safe Room Rebate Program is a model for supporting the construction of safe rooms through the Hazard Mitigation Grant Program Grants,” said FEMA spokesman Dan Watson.

Localities can also apply for another pool of federal money, as the City of Moore was attempting to do. Moore wanted $2 million in rebates for 800 homeowners to build safe rooms, and had submitted an emergency plan to the state and FEMA as part of the application process. But according to the city’s website, changes in federal regulations created a “moving target” and delayed the program.

FEMA’s Watson said that in the past 20 years, “FEMA has invested more than $57 million in 11,768 private and public safe rooms in Oklahoma, more structures than any other state. Many were in the same area as yesterday’s tornado.”

“The State of Oklahoma has been a great partner in providing innovative mitigation solutions to residents,” he added.

Despite the construction and subsidies, Bennett estimated that less than a fifth of the state’s 4 million residents have access to meaningful private shelter from tornadoes. In Moore, according to the New York Times, only about 10 percent of homes have them.

TODAY's Matt Lauer speaks with the firefighters and police officers who are searching through what's left of Plaza Towers Elementary School in Moore, Okla., after it was hit by a tornado on Monday afternoon, resulting in the deaths of seven children.

Schultz, the Kansas architect, said Oklahoma schools are not required to have storm shelters, but can apply for federal funding to build them. Albert Ashwood, who heads the Oklahoma Department of Emergency Management, said at a press conference Tuesday that safe rooms at more than 100 schools had been funded via FEMA, but that the two schools hit in Oklahoma, Briarwood Elementary and Plaza Towers Elementary, were not among them. There are more than 1,800 public schools in Oklahoma.

“You have limited funds that are based on disasters you’ve had in the past,” he said. “When you have limited funds, you set priorities on what schools you want to ask for.”

He also said that his department was trying to determine how many schools in the state had safe rooms.

The preference for safe rooms in private residences rather than public structures is only partly about political philosophy. It’s also based on a safety calculation. Using your own shelter or a neighbor’s shelter can be faster than trying to reach a central location.

“I don’t think it’s a good idea to drive across town when there’s a tornado,” said Bennett. “That’s where community shelters fall short.”

On the City of Moore’s website, an Emergency Management notice explains that Moore has no community shelter because there is no building suitable for one, and because “overall, people face less risk by taking shelter in a reasonably well-constructed residence!”

Next door in Kansas, however, Schultz says an equally beet-red state seems to have decided to steer its disaster money to creating more public shelters. Schultz says that his state, like Oklahoma, depends on FEMA funding for tornado shelters, but has focused on adding safe rooms to schools. In 1999, tornadoes hit schools in Wichita, and though no one was killed, “that opened eyes.”

“When we send our kids to school there are two things we take for granted,” said Schultz. “One is that they’re learning something. The other is that they’ll come home safe. “

“The Enterprise tornado and now this tornado show us that’s not always the case. I truly believe in shelters in schools for that reason.”

Bennett said that he is now receiving the same kind of back-channel signals that he got after the 2007 tornado in Enterprise, Ala., where a tornado killed seven at the local high school. That led Alabama to require schools to include safe rooms or to close during tornado watches. “Oklahoma may be headed in the direction of Alabama,” he said.

On Wednesday, Moore mayor Glenn Lewis said he would propose a new ordinance requiring shelters in newly constructed single and multi-family homes. "We'll try to get it passed as soon as I can," he told CNN.

And Chris Shatswell, an Oklahoma native who now lives in Fort Worth, Texas, has created an online petition via Change.org to get storm shelters in Oklahoma schools.

So while Morrissette, the Oklahoma legislator, worries that the current attention to increasing the supply of shelters may be short-lived, Bennett is more optimistic. “This has a shelf-life. The story of the kids in Moore has an impact,” he said.

Mark Schone is an investigative editor for NBC News; Nidhi Subbaraman is a contributing technology and science writer for NBC News; Alan Boyle, NBC News Digital science editor, also contributed to this report.